‘Green-tea’ extract soldered triple interpenetrating polymer network membranes for water remediation

Abstract

Commercial state-of-the-art membranes are generally plagued by the counterposition of permeability and selectivity. Additionally, fouling and scaling issues coupled with linear lifecycles and high energy consumption further intensify the impairment of membrane performance. Hence, superior antifouling membranes with a significant balance of water permeance and separation abilities continues to be at the core of the current research epicenter. Herein, inspired by nature, we electrostatically soldered 'green tea' extract epigallocatechin gallate (EGCG) with the membrane's key ingredients (doped aniline and pyrrole) to aid in the hydrophilic features and render the membranes antifouling. The doped monomers are then polymerized as polyaniline and polypyrrole in-situ in polyvinylidene fluoride (PVDF), evolving into triple interpenetration polymer networks (IPNs), which facilitates pore tightening and molecular sieving. The highly negative surface charge, due to –OH functional groups in EGCG, also aids in antifouling performance and rejects organic dyes from contaminated water. This triple IPN membrane exhibited excellent mechanical and thermal stability -a key requirement for sustainability. The membrane shows steady performance for multiple operating cycles in terms of salt rejection (ca. 98% for monovalent and > 99% for divalent) and dye removal (ca. 99%) for both cationic and anionic dyes besides being chlorine tolerant. The rationale behind choosing ‘green tea’ extract is also to harness antimicrobial properties in the membrane. The EGCG based triple IPN membranes showed excellent antibacterial (>6.908 log reduction) and antiviral properties (∼2.3 log reduction) besides being non-cytotoxic against mammalian cell lines - a key requirement when they are disposed of in the landfill. The strategy adopted here paves the way for next generation membranes for water remediation and will help guide the researchers working in this domain from both academia and industry.